Implant for fixing femoral fractures

ABSTRACT

The present implant is for fixing femoral fractures and the like. The implant consists of three main parts, namely a first part consisting of an angle element, a second part which forms a holder and a third part in the form of a screw. The angle element includes a sleeve for receiving the screw. Both the sleeve and the screw are intended to be passed into a channel provided through the neck and head of the femur of a patient. The angle element moreover includes a slide which is slidingly accommodated by the holder. The holder is, in its turn, secured by means of anchorage screws in the shaft of the femur. By cooperation between the slide and the holder the possibility is afforded that the angle element may move in relation to the shaft of the femur. The sleeve of the angle element is disposed at an angle in relation to the slide.

"This is a continuation of application Ser. No. 08/835,546 filed on Apr.8, 1997 (now U.S. Pat. 5,728,099 issued Mar. 17, 1998) which is acontinuation of Ser. No. 08/332,890 filed Nov. 1, 1994 (now abandoned),claims the benefit thereof and incorporates the same by reference."

FIELD OF THE INVENTION

The present invention relates to implants for fixing femoral fractures

BACKGROUND

The term femoral fractures is here taken to signify intertrochanterian,subtrochanterian and supracondylar fractures, i.e. fractures atdifferent places of the thigh bone (femur).

In order to promote the healing of femoral fractures, use has been madefor a relatively long time of various types of screws or pins for fixingthe loose bone pieces in such mutual positions that the growing togetherof the bone pieces across the sides of the fracture is promoted.

In intertrochanterian fractures or fractures which are bothinter-trochanterian and subtrochanterian, the orthopedist has, tosupport the bone pieces around the fracture, often chosen in accordancewith techniques hitherto employed to use a fixation device (implant)comprising a screw and an angled plate with which the screw isconnected. The screw is passed, via a bore, into the head of the femurand is thereafter screwed in place therein. The plate is secured to thefemur by means of screws of considerably smaller dimensions than thepreviously mentioned screw. The head of the femur and the femur properhave thereby obtained mutually fixed positions even if the fixationdevice permits a certain, very limited possibility for sliding in thelongitudinal direction of the neck of the femur. On the other hand, theplate secured to the femur has always been arranged to realize acompletely rigid fixation of the plate in the longitudinal direction ofthe femur.

While operations in which such fixation devices are applied normallygive the desired outcome, it is not uncommon that problems occur becauseof excessive loading on the fixation device. Excessively high loadingentails, for example, that the plates or their anchorage screws breakoff, that the smaller anchorage screws are projected out of their holesin the bone some time after the operation or that the large screw upthrough the neck of the femur cuts through the surface definition of thehead of the femur towards the hip joint. Such problems are naturallyextremely negative, involve pain to the patient and often entail that anew operation must be carried out.

Moreover, the technique disclosed in the immediately precedingparagraphs entails the disadvantage that the fracture surfaces afterbeing subjected to loading, are occasionally fixed in positions in whichthe surfaces do not fit into one another, a factor which both prolongsand impedes the healing process. This results in bone shortening,lameness and difficulties in walking.

SUMMARY OF THE INVENTION

The implant according to the present invention eliminates theabove-indicated disadvantages inherent in prior art employed implantsand makes it possible better to utilize the natural healing processes ofthe human body. The implant also entails that the body, when necessary,corrects the mutual positions of the fracture pieces so that thefracture pieces, once the operation has been completed and the patientsubjects the area to load by walking, assume more optimum positionsfavorable for the process of healing and growing together. This iseffected in that the implant is of a construction which permits bothcontraction and separation movements in the axial direction of the shaftof the femur and in the direction of the hole made in the head of thefemur. In addition, the implant according to the present inventionpermits movements transversely of the longitudinal direction of theshaft of the femur to a degree which corresponds to a maximumdisplacement of the fracture surfaces in relation to one another of upto between 5 and 7 mm.

It is not only those forces which occur in normal loading to which theimplant is subjected. When the patient is anaesthetized during theoperation, the muscles are wholly relaxed, but when the patient recoversfrom the anaesthetic after the operation, considerable muscularcontractions take place. This causes considerable compression forces onthe fracture. In such an event, these forces are directed substantiallyalong the axial direction of the shaft of the femur. The implantaccording to the present invention is of such construction that thosemovements caused by the muscular contraction are absorbed and controlledby the implant.

As was mentioned above, it is important that the implant permitsmovement along the shaft of the femur. The only type of angled implantfor fractures of the femur of which we are aware and which permits thesliding movement disclosed by way of introduction is disclosed in U.S.Pat. No. 4,628,923. However, the sliding movement is restricted by theuse of a distal screw. No movement transversely of the direction of theshaft of the femur is either mentioned or intimated in the patentspecification. The above-described sought-for function in the implant isachieved according to the present invention by providing relativemovement of respective slidable portions of a holder anchored to thefemur and of a slide carrying an anchorage screw also anchored to thefemur. The holder and slide are not directly connected to one another sothat their sliding portions can move relative to one another andaccommodate changes in the femur during loading thereof.

Applying the solution according to the present invention, there will beobtained an implant which is flexible in that it can be employed in manydifferent fracture formations, and in which the natural healing powersof the human body are supported instead of, as is sometimes the case inthe employment of prior art implants, impeding and obstructing thenatural healing conditions.

In order to create as small an operation incision as possible, theportion fixed to the shaft of the femur must have as slight axial extentas possible in the longitudinal direction of the shaft of the femur.

The implant according to U.S. Pat. No. 4,628,923 suffers from thedrawback that the operational incision will be relatively long, sincethe implant is of a construction which requires that the operationincision be made longer than the retainer element itself. The reason forthis long operational incision is that there must be room to allow foroperating a compression screw or so-called distal screw disposed in theaxial direction of the retainer element, which lengthens the operationalincision by approx. 5 cm or more. Yet a further disadvantage is that thelocking of the rotational movement between the cooperating parts of theimplant is complicated, in that the circular cross-section necessitatesa solution in which rotational movements are prevented, this beingattained in the patent by means of a tongue and groove.

In one embodiment of the implant according to the present invention, theimplant has a construction which entails that, when it is to bridge overa certain length of the shaft of the femur, the advantage will beattained that the requisite length of the implant is less than thelength which is required in the implant according to U.S. Pat. No.4,628,923. This is achieved in that the sliding portion of the secondpart is disposed to permit the lower end of the sliding portion to passthe lower end of the sliding portion of the second part.

There is a series of, to some extent contrary, demands placed on animplant for fixing femoral fractures. The basic requirement is that theimplant must be sufficiently powerful in order to be able to absorbthose forces to which it is expected to be subjected, without riskingbreakage. For the orthopedist, it is important that the implant issimple to handle so that he/she can quite simply concentrate on applyingit in place. In an alternative embodiment of the present invention theimplant is, therefore, arranged so as to permit the mutually slidingparts, to be temporarily and adjustably fixed to one another until theimplant is in place.

There are further requirements that the implant should follow andconnect as closely as possible to the bone and project out as little aspossible from the femur, in order that the patient does not suffer fromgreater discomfort than is absolutely necessary.

In order, if possible, to avoid the risk that the orthopedist places thedifferent implant parts too far apart, which could result in such largetorque forces being applied that there is a risk of breakage, theimplant is, in one embodiment, provided with a mechanical stop whichprevents sliding movement past a certain critical position. In onealternative embodiment, the point which may not be passed on a slidingmovement is shown by markings.

Yet a further advantageous feature of the implant according to thepresent invention is that the retainer plate is designed so that thescrews which are secured in the femur will be in place crosswise, whichimproves stability.

BRIEFDESCRIPTION OF THE DRAWINGS

The present invention will now be described in greater detailhereinbelow, with the aid of embodiments shown on the drawings. In theaccompanying drawings:

FIG. 1 is a top plan view of one embodiment of the implant;

FIG. 1a is a top plan view illustrating the movability of the implant;

FIG. 2 is an exploded view of the apparatus of FIG. 1 seen from theside;

FIG. 3 is a cross-sectional view taken along the line III--III in FIG. 1or FIG. 1a;

FIG. 4 is an end elevation of one of the details in the embodiments ofFIG. 1 or FIG. 1a;

FIGS. 5a,b, 6a,b show different methods of arranging temporary lockingof the sliding movement between the different parts included in theembodiments according to FIG. 1 or FIG. 1a;

FIG. 7a is a detailed view of a locking device;

FIG. 7b is a detailed view of the placing of markings;

FIG. 8 is a cross-section corresponding to that of FIG. 3 of analternative embodiment;

FIG. 9 shows an implant according to the present invention fixed to thefemur;

FIG. 10 is a cross-section taken along the line X--X in FIG. 9; and

FIG. 11 is a top plan view of an alternative embodiment of the implant.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the embodiment shown in the FIGS. (cf. FIGS. 1 and 2), the implantconsists of three main parts, namely a first part constituting an angleelement 1, a second part forming a holder 2 and a third part in the formof an anchorage device 3 and shown in the FIG.s in one preferredembodiment in which it is in the form of a screw (lag screw) 3,hereinafter designated main screw 3.

The angle element 1 has a first section which substantially consists ofa sleeve 10, and a second section which substantially consists of aslide 11. In the region 14 where the sleeve 10 merges into the slide 11,the angle element 1 displays a portion 16 which is thickened in relationto the slide 11. The thickened portion forms the upper region of theslide. The central cavity 13 of the sleeve 10 is arranged to receive themain screw 3 preferably with tight fit. One opening 47 of the centralcavity is located in the thickened portion 16. The slide 11 is intendedto be disposed substantially parallel with the shaft of the femur. Thesection between the transitional region 14 and the lower end 15 of theslide forms the sliding portion 11 of the first part 1.

The sleeve 10 is disposed at an angle α in relation to the slide (cf.FIG. 2). Normally, the angle cc is of the order of magnitude of between120-150°. Preferably said angle α varies between 130° and 140°, and, asa rule is approx. 135°. In other embodiments intended for special typesof fractures and bone sizes, the angle α varies further.

As is apparent from FIG. 3, the slide 11 has, in the illustratedembodiment, sloping side walls 12 where the width of the slide 11surgically inserted with the implant decreases in a direction away fromthe femur.

In the embodiment illustrated in FIGS. 1,1a and 9, the holder 2 displaysa groove 21 (cf. FIG. 4) of a cross-sectional configuration whichcorresponds to the cross-sectional configuration of the slide 11, i.e.the groove displays side walls 22 which slope towards one another. Thegroove 21 forms the sliding portion 21 of the second part 2. The holder2 moreover has a number of flange portions 24 through which holes 25 areprovided for receiving screws 5 which are intended to be secured in thefemur. These screws are of smaller dimensions than the main screw 3 andare hereinafter generally referred to as anchorage screws 5. The groove21 on the holder 2 is throughgoing, i.e. it has no stop abutment at theends of 20,23 the groove whereby the entire groove length in thisembodiment can be utilized for accommodating the slide 11, which entailsthat the operational incision will be kept short. The absence of stopabutments entails that one and the same holder 2 can be employed forangle elements 1 with different lengths of the slide 11.

The holder 2a according to the embodiment in FIG. 11 differs from theholder 2 according to the above-described embodiment only in that thegroove 21a is closed at the lower end 23a. A distal screw 48 passesthrough a bore in the lower end 23a of the holder and is received in athreaded bore 49 in the lower end 15a of the slide 11a. The head of thedistal screw abuts against the lower edge of the holder, whereby theslide 11a is displaced upwardly or downwardly in the groove 21a of theholder 23a when the screw is rotated, and therewith the sleeve 10 of theangle element 1. Other reference numerals have their counterparts inthose previously defined in the description of FIGS. 1-10. This type ofholder is employed, for example, if there is a need for an implant whichmakes it possible to apply a compression force in the axial direction ofthe shaft of the femur.

The axial length of the holder 2 is, in the embodiment illustrated inFIGS. 1,1a,9 and 10, shorter than the axial length of the slidingportion 11 of the first part, whereby the operational incision can bekept short. A further feature of the illustrated embodiment which makespossible short operational incisions is that the hole 25 for thelower-most anchorage screw 5 is disposed a distance from the lower edge23 of the holder 2. The operational incision need not be longer than itprovides access for screwing in the lowermost anchorage screw 5. Thoseparts of the implant which are located lower down can be moved intoplace without needing to make an incision for the region below thelowermost anchorage screw 5. This is effected in that the tissue istemporarily lifted up below the region of the lowermost screw,whereafter the implant is passed in beneath the raised tissue.

Even though the holders 2,2a are provided, in the illustratedembodiments, with holes 25 for four or six anchorage screws 5, thepresent invention is not restricted to implants exclusively includingholders having this number of holes. If necessary, a larger number ofholes, for example 8 or 10, and so on, may be employed.

In the illustrated example, the anchorage means consist of the mainscrew 3 with a thread 31 and a shaft 32 which fit into the sleeve 10.The screw 3 is disposed, if desired, to be lockable in relation to thesleeve 10 with the aid of a clamping screw 4 which is screwed into athreaded opening (not shown) in the end of the screw shaft 32. Theillustrated screw 3 should only be seen as an example of one embodiment,and given that the invention is not dependent upon the exact design ofthe screw 3, this will not be described in greater detail. It is obviousthat the anchorage device may be of varying designs, for example a nail,a pin, a bolt provided with projecting anchorage means in its end, etc.

FIG. 9 shows one example of how an implant according to the invention isfixed at the femur in a femoral fracture comprising both anintertrochanterian fracture 42 and a subtrochanterian fracture 43. As isapparent from the FIG., the main screw 3 is secured in a channel throughthe neck of the femur 44 and the head of the femur 41, and the holder 2is fixed with the aid of anchorage screws 5 in the shaft 40 of thefemur.

FIG. 1a illustrates one embodiment of the invention in which thecrosssection of the sliding portion 21 of the holder 2 and the slidingportion 11 of the angle element 1 are dimensioned such that there existsa certain clearance between both of the sliding portions. The conicalcross sections entail that this clearance is at its greatest when theslide 11 is most proximal the bottom 46 of the groove 21. Thedimensional differences of the cross-sections are selected such that themaximum permitted displacement of the opening 47 from a neutral positioni.e. when the sliding portions 11 and 21 are aligned and centered, isless than approx. 7 mm and as a rule approx. 5 mm. The clearance whichis required for sliding to occur is normally approx. 0.02 mm.

By cooperation between the sliding portion 11 of the slide and thesliding portion 21 of the holder 2, it is possible that the angleelement 1 can move axially along the shaft of the femur 40. In theembodiment illustrated in FIG. la, a certain limited movement is alsomade possible in a plane substantially at right angles to the axialdirection of the slide. The parts are manufactured from a material whichgives low friction between the different sliding portions of the parts,for example surface-treated stainless steel.

The movement transversely of the shaft of the femur 40 is illustrated inFIGS. 1a and 11 by broken lines 52,52a. It will be obvious to a personskilled in the art that the broken lines 52,52a merely indicate one ofthe possible directions of movement transversely of the axial directionof the slide. In those embodiments in which the construction of theimplant permits movements transversely of the axial direction of theslide, such movement takes place in that direction occasioned by therelevant loading of the implant.

When applying the implant, a channel is first drilled in the head 41 ofthe femur in which channel the main screw 3 (according to theillustrated embodiment) is passed once threads have been formed by athreaded pin on the inner wall of the channel. This is often preceded(among other things in order to check the direction and alignment of thechannel) by the drilling of a small hole, whereafter a guide wire ispassed in and up through the head of the femur. In order to be able touse this technique, the screw 3 is normally provided with an axialthrough aperture. When the channel has been drilled and the entry holebroadened in the radial direction to receive the sleeve, and once themain screw 3 has been screwed into the head 41 of the femur, the sleeve10 is passed in onto the screw shaft 32.

The next step for the orthopedist is to determine where the holder 2 isto be placed in order to provide maximum support but nevertheless makepossible sufficient sliding along the sliding portion 21 of the holder.When this position has been determined, holes are drilled for theanchorage screws 5 in the shaft 40 of the femur, whereafter theanchorage screws 5 are screwed in place in order to fix the holder 2 inrelation to the shaft 40 of the femur. Before the holder 2 is finallyfixed at the shaft 40 of the femur, a locking screw 4 may, if this isconsidered necessary, be screwed into the bottom of the screw 3 insertedin the head of the femur.

Forces are normally exercised on the femur substantially in twodirections, partly in the major direction of the head and neck of thefemur (which are guided via the screw 3 and the sleeve 10 inserted inthe head 41 of the femur), and partly along the shaft 40 of the femur.The forces in a direction of the head and neck of the femur are guidedvia the main screw 3 and the sleeve 10, and the forces along the shaft40 of the femur are guided by the sliding portions 11 and 21 of theholder 2 and the angle element 1. The muscular contraction which takesplace when the patient recovers from the anaesthetics exerts arelatively powerful compression in the direction of the shaft 40 of thefemur.

Movements along the shaft 40 of the femur occur on healing as a ruleamounting to several cm and normally lie in the range of between 0-2 cm.The movement transversely of the shaft of the femur is substantiallyless and lies normally in the range of between 0-8 mm.

The implant according to the invention unites the requirement ofstability of the implant with the requirement on restrictive movementbetween the meeting surfaces of the fracture. Thus, employment of theimplant affords the post-operative possibility of permitting a movement,between the fracture surfaces, predetermined by the orthopedist, in thelongitudinal direction of the shaft of the femur and a mobility,determined by the dimensions of the implant, transversely of thelongitudinal direction of the shaft of the femur. Since minor movementsin a fracture promote the healing process, the above-disclosed movementsin the longitudinal and lateral directions entail that a stimulation ofthe healing process is achieved. It should be particularly noted thatthe above-disclosed movements in the lateral direction afford thepossibility of rectifying the fracture surfaces so that these mutuallyadapt and assume a well compressed position for the fracture, at thesame time as the pumping effects occurring on movement between thefracture surfaces is utilized to the full for promoting the healingprocess.

In certain practical applications, it is desirable to restrict themaximum downward sliding of the angle element 1 in relation to theholder 2. The thickened portion 16 in the transitional region 14 of theangle element 1 restricts the upward movement of the holder 2 towardsthe main screw 3. When this stop function is to be employed, theorthopedist places the holder 2 in such a position that the distancebetween the upper edge 20 of the holder and the thickened portion 16 ofthe angle element 1 corresponds to the length of the maximum movementwhich can be permitted in the longitudinal direction of the shaft of thefemur.

Given that the side of the holder 2 which is intended to be turned toface towards the shaft 40 of the femur including the flange portions 24of the holder is of concave form, the anchorage screws 5 may, afterapplication, be disposed crosswise in the shaft 40 of the femur. (FIG.10).

In order, in an operation, that the holder 2 and the angle element 1 arenot unintentionally separated from one another before the implant isapplied, a stop device is provided in certain embodiments, which atleast temporarily fixes the slide 11 of the angle element 1 in relationto the holder 2.

In embodiments according to FIG. 5, the fixing disclosed in thepreceding paragraph is effected by means of a locking screw 6 which isaccommodated in a threaded through aperture 45 in the slide 11. Thetemporary locking is effected in that the locking screw 6 is screwedinto contact the bottom of the groove 21 of the holder 2, the slidebeing raised from the bottom and pressed against and locked by thesloping side walls 22 of the groove. In one alternative application,locking is effected in that the locking screw 6 is screwed in only sofar that its tip projects out beneath the slide 11 when the aperture 45is located beneath the lower edge 23 of the holder 2. The concept hereis that the locking screw 6 is backed off once the implant has been inthe femur.

In the embodiment according to FIG. 6a, locking of the angle element 1takes place with the aid of friction, in that the side walls 12 and 22of each respective sliding portion 11, 21 are provided with frictionsurfaces 19. Only the friction surface on the slide 11 is shown in FIG.6a.

In alternative embodiments, the temporary locking is provided with theaid of rubber plugs, etc.

In a further alternative embodiment, locking is effected by means of aball resiliently depressed into an opening in the bottom of the groove21. The ball forces the side walls 12 of the slide 11 upwards towardsthe side walls 22 of the groove 21 with a force which is sufficient toprevent sliding movements between the sliding portions 11,21.

In yet a further alternative embodiment shown in FIG. 6b, the ball isreplaced by a plate 50 tension by springs 51. The upwardly directedforce on the slide 11 is, in the two above-disclosed embodiments,sufficiently great for the parts not to become separated by the actionof, for example, force of gravity but is not so great that the parts areprevented from being displaced in relation to one another in the normalmuscular and loading forces which prevail as described above.

In one alternative embodiment, the angle element 1 displays a groovewhich surrounds a ridge-like elevation 29 on the holder 2, the grooveand the elevation 29 forming the sliding portions (FIG. 8).

If the holder 2 is placed too far down on the shaft 40 of the femur,there is a risk that the end 15 of the slide 11 will be so high in thegroove 21 that the abutment between the side walls 12,22 is insufficientto withstand the torque forces which occur, in which event either theholder 2 or the slide 11 will break. In order to prevent this, amechanical abutment is provided in certain embodiments, this preventingthe end 15 of the slide 11 from coming too high in the groove 21. In theembodiment according to FIG. 7a, this abutment consists of aspring-pretensioned 26 pin 27 which cooperates with a locking aperture17 in the slide 11. This locking arrangement may also function as atemporary stop for inadvertent sliding movements in accordance with theabove.

Instead of a mechanical stop member, the slide 11 and the holder 2 have,in the embodiment shown in FIG. 7b, been provided with markings 18,28which must not pass one another in order to avoid the risk of breakageof the implant as contemplated above. The markings consist of scribings,scorings, inlays of different colors, etc. In one alternativeembodiment, only one of the sliding portions 11,22 is provided with amarking, while the end of the other sliding portion constitutes a secondmarking.

In the above description of the illustrated embodiment, we have taken asa point of departure the situation when the implant is employed forfixing intertrochanterian 42 and subtrochanterian 43 fractures. As wasdisclosed in the introduction of the specification, the implantaccording to the present invention can also be employed forsupracondylar fractures, in which event the sleeve 10 will, however, bedisposed further down, the angle a being then between 80° and 100°.Preferably, the angle α varies between 90° and 100°, and, as a rule isapprox. 90°.

When use is made, in the body of this description, of expressions suchas upper, lower, etc., these generally relate only to those directionsin the FIGS. to which they refer.

Even though the description above has concentrated on femoral fractures,it will be obvious to a person skilled in the art that the implantaccording to the present invention is conceivable for use also infractures to other bones, such as bones of the lower leg and theforearm.

What is claimed is:
 1. An implant for fixing femoral fractures comprising a first part, a second part and an anchorage device; said first part including a sleeve for receiving said anchorage device, said sleeve being adapted for insertion in a channel provided in the head of a femur, said first part further including a slide, said sleeve being permanently fixed at an angle to said slide and including a throughgoing central cavity with an opening facing towards said slide, said slide being intended to be disposed in a longitudinal direction along the shaft of the femur and forming a sliding portion; said second part including a sliding portion which is axially and slidably engaged with said sliding portion of said first part, said second part having apertures located laterally outside said sliding portion of the second part for receiving anchorage screws intended to be secured in the shaft of the femur; said anchorage device being adapted for being secured in the head of the femur and disposed to be received by said sleeve, said first and second parts being respectively securable to the femur by said anchorage device and by said anchorage screws such that said sliding portions of said first and second parts are free to undergo relative axial and sliding movement in response to load applied to the femur, wherein said sliding portions are engaged with transverse clearance to permit movement relative to one another transversely of the longitudinal direction of the shaft of the femur by a restricted amount to provide maximum transverse displacement of said opening of said central cavity of about 7 mm from a neutral position in which the sliding portions of said first and second parts are longitudinally aligned and centered.
 2. The implant as claimed in claim 1, wherein said sliding portion of said second part is formed by a groove open at both its ends; and the slide of said first part includes, in a transitional region to said sleeve, a cross-sectional alteration which, at a predetermined position, prevents continued relative sliding movement of said sliding portion of said second part in a direction towards said sleeve.
 3. The implant as claimed in claim 1, wherein said second part comprises a holder provided with said sliding portion in the form of a groove which is upwardly open; said groove is extended along the entire axial extent of said holder; said groove of said holder having, in cross-section, sloping inner side walls which form the sliding surfaces of the second part, said groove having a width between said walls which decreases upwardly; said sliding portion of said first part having a cross-sectional configuration with sloping side walls which form the sliding surfaces of the first part slidably fitted in said groove in said holder with said transverse clearance to permit the relative movement of said sliding portions and said transverse displacement of said sliding portions.
 4. The implant as claimed in claim 1, wherein a groove is provided in said slide of said first part, said groove receiving said sliding portion of said second part for said relative transverse displacement as well as relative longitudinal displacement.
 5. The implant as claimed in claim 1, comprising an arrangement for temporarily fixing said sliding portion of said first part in relation to said sliding portion of said second part, and means for preventing said sliding portions of said first part and said second part from sliding apart.
 6. The implant as claimed in claim 5, wherein said arrangement for temporarily fixing said sliding portions of said first and second parts comprises a locking screw, and an aperture for receiving said locking screw disposed adjacent to a lower end of said sliding portion of said first part, said aperture being oriented such that a tip of said locking screw locks against said sliding portion of said second part.
 7. The implant as claimed in claim 5, wherein said arrangement for temporarily fixing said sliding portions of said first and second parts comprises friction surfaces disposed on sides of said sliding portions of said first and second parts facing one another.
 8. The implant as claimed in claim 5, wherein said arrangement for temporarily fixing said sliding portions of said first and second parts comprises a spring-tensioned pin on said sliding portion of one part which bears against said sliding portion of the other part.
 9. The implant as claimed in claim 5, wherein said means for preventing said sliding portions from sliding apart comprises a spring-tensioned pin on said sliding portion of one part which cooperates with an aperture in said sliding portion of the other part.
 10. The implant as claimed in claim 5, wherein said means for preventing said sliding portions from sliding apart comprises marking means on each respective sliding portion of said first and said second parts to indicate positions beyond which said sliding portions are not to pass one another.
 11. The implant as claimed in claim 1, wherein the axial extent of said second part is equal to or less than the axial extent of said sliding portion of said first part.
 12. An implant for fixing femoral fractures comprising a first part, a second part and an anchorage device; said first part including a sleeve for insertion in a channel provided in the head of a femur, said first part further including a slide, said sleeve being permanently fixed at an angle to said slide, said slide being intended to be extended along a longitudinal direction of the shaft of the femur and forming a sliding portion; said second part including a sliding portion which has sliding surfaces axially and slidably engaged with sliding surfaces of the sliding portion of said first part, said second part having apertures located laterally offset from said sliding surfaces of said second part for receiving anchorage screws intended to be secured in the shaft of the femur; said anchorage device being adapted for being secured in the head of the femur and disposed to be received by said sleeve, said slide having a lower end which can freely pass a lower end of said sliding portion of said second part; said slide having, in a transitional region to said sleeve, a cross-sectional alteration which, at a predetermined position of said sliding portions prevents continued relative sliding movement of said sliding portion of said second part in a direction towards said sleeve, said first and second parts being respectively securable to the femur by said anchorage device and by said anchorage screws and being slidably connected to one another by said sliding surfaces of said first and second parts so that said sliding portions of said first and second parts are free to undergo relative axial sliding movement in response to load applied to the femur.
 13. The implant as claimed in claim 12, wherein the sliding portion of said second part is formed by a groove open at both its ends.
 14. The implant as claimed in claim 12, wherein said second part comprises a holder with said sliding portion thereof in the form of a groove which is upwardly open; said groove is extended along the entire axial extent of said holder; said groove in said holder having, in cross-section, sloping inner side walls which form said sliding surfaces of said second part, said groove having a width between said side walls which decreases upwardly; said sliding portion of said first part having a cross-sectional configuration with sloping side walls forming the sliding surfaces of said first part and which are slidably fitted in said groove in said holder.
 15. The implant as claimed in claim 12, wherein a groove is provided in said slide of said first part, said groove slidably receiving said sliding portion of said second part.
 16. The implant as claimed in claim 12, comprising an arrangement for temporarily fixing said sliding portion of said first part in relation to said sliding portion of said second part, and means for preventing said sliding portions of said first part and said second part from sliding apart.
 17. The implant as claimed in claim 16, wherein said arrangement for temporarily fixing said sliding portions of said first and second parts comprises a locking screw, and an aperture for receiving said locking screw disposed adjacent to a lower end of said sliding portion of said first part, said aperture being oriented such that a tip of said locking screw locks against said sliding portion of said second part.
 18. The implant as claimed in claim 16, wherein said arrangement for temporarily fixing said sliding portions of said first and second parts comprises friction surfaces disposed on sides of said sliding portions of said first and second parts facing one another.
 19. The implant as claimed in claim 16, wherein said arrangement for temporarily fixing said sliding portions of said first and second parts comprises a spring-tensioned pin on said sliding portion of one part which bears against said sliding portion of the other part.
 20. The implant as claimed in claim 16, wherein said means for preventing said sliding portions from sliding apart comprises a spring-tensioned pin on said sliding portion of one part which cooperates with an aperture in said sliding portion of the other part.
 21. The implant as claimed in claim 16, wherein said means for preventing said sliding portions from sliding apart comprises marking means on each respective sliding portion of said first and said second parts to indicate positions beyond which said sliding portions are not to pass one another.
 22. The implant as claimed in claim 12, wherein the axial extent of said second part is equal to or less than the axial extent of said sliding portion of said first part. 